The present invention relates to semiconductor devices including capacitors, especially capacitors in which ferroelectrics or high-xcexa materials are used for capacitive insulating films, and methods for fabricating the same.
Ferroelectrics or high-xcexa materials exhibit remanent polarization due to hysteresis properties or high relative dielectric constants. Thus, in the field of nonvolatile memories or DRAM devices, the ferroelectrics or the high-xcexa materials can substitute for silicon oxide or silicon nitride used for capacitive insulating films included in capacitors of semiconductor devices.
Hereinafter, a known method for fabricating a semiconductor device including a capacitor in which a ferroelectric or a high-xcexa material is used for a capacitive insulating film will be described with reference to the drawings.
First, as shown in FIG. 19A, a transistor region 103 is defined by an isolation film 102 selectively formed in a semiconductor substrate 101 of silicon. Thereafter, an MOS transistor 104 is formed in the transistor region 103.
Next, as shown in FIG. 19B, a first interlevel dielectric film 105 of silicon dioxide is deposited, and then the surface thereof is planarized. Thereafter, a lower-electrode formation film of platinum is deposited by a sputtering process on the planarized first interlevel dielectric film 105. Subsequently, a ferroelectric film containing strontium, bismuth, tantalum and the like is formed by a spin-on process on the lower-electrode formation film. After the ferroelectric film has been crystallized, an upper-electrode formation film of platinum is deposited by a sputtering process on the ferroelectric film. Thereafter, the upper-electrode formation film, the ferroelectric film and the lower-electrode formation film are dry-etched in this order, thereby forming a lower electrode 106, a capacitive insulating film 107 and an upper electrode 108 out of the lower-electrode formation film, the ferroelectric film and the upper-electrode formation film, respectively, on part of the interlevel dielectric film 105 located over the isolation film 102. In this manner, a capacitor 109 made of the lower electrode 106, the capacitive insulating film 107 and the upper electrode 108 is formed.
Then, as shown in FIG. 19C, a second interlevel dielectric film 110 of silicon dioxide is deposited over the entire surface of the semiconductor substrate 101. Thereafter, a first contact hole 110a for exposing the upper electrode 108 therein and a second contact hole 110b for exposing a doped region of the MOS transistor 104 therein are formed in the second interlevel dielectric film 110.
Then, as shown in FIG. 19D, a metal film containing aluminum as a main component is deposited over the entire surface of the second interlevel dielectric film 110 including the contact holes 110a and 110b. The metal film is patterned, thereby forming a wiring 111 out of the metal film. Thereafter, another wiring layer and a passivation film, for example, are formed.
In the known method for fabricating a semiconductor device, however, the capacitor 109 is formed over the isolation film 102 adjacent to the transistor region 103.
In addition, since the capacitor 109 extends along the principal surface of the semiconductor substrate 101, i.e., has a so-called planar structure, the projected area of the capacitor 109 onto the substrate surface that is enough to ensure a required capacitance is large, resulting in the extremely small effect of reducing a wiring rule for the MOS transistor 104 and the wiring 111.
Therefore, especially the semiconductor device including the capacitor 109 in which a ferroelectric or a high-xcexa material is used for the capacitive insulating film 107 has a problem that the area of each capacitor, specifically the area of each cell in a semiconductor memory, cannot be reduced.
It is therefore an object of the present invention to reduce the area of each capacitor in a semiconductor device including a capacitor.
In order to achieve this object, according to the present invention, an oxygen barrier film, a lower electrode and a capacitive insulating film are stacked over a conductive plug, and in addition, the capacitive insulating film has a bent portion that extends along the direction of penetration of the conductive plug.
Specifically, a first inventive semiconductor device includes: a conductive plug formed through an insulating film; a conductive oxygen barrier film formed on the insulating film so as to be electrically connected to the conductive plug and to cover the conductive plug; a lower electrode formed on the oxygen barrier film and connected to the oxygen barrier film; a capacitive insulating film formed on the lower electrode, following the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has a bent portion that extends along the direction in which the conductive plug penetrates through the insulating film.
In the first inventive semiconductor device, the capacitor made of the lower electrode, the capacitive insulating film and the upper electrode is formed over a transistor with the conductive plug sandwiched therebetween. Thus, the unit area of a cell constituted by the capacitor and the transistor is reduced. In addition, since the capacitive insulating film has the bent portion that extends along the direction of penetration of the conductive plug, the capacitive insulating film has a face substantially perpendicular to the substrate surface. Accordingly, the projected area of the capacitive insulating film onto the substrate surface is reduced, thus further reducing the cell area. Moreover, since the oxygen barrier film is interposed between the lower electrode and the conductive plug, the conductive plug is not oxidized by oxygen atoms constituting the capacitive insulating film.
A second inventive semiconductor device includes: a conductive plug formed through a first interlevel dielectric film formed on a substrate; a conductive oxygen barrier film formed on the first interlevel dielectric film so as to be electrically connected to the conductive plug and to cover the conductive plug; a second interlevel dielectric film formed on the first interlevel dielectric film and having an opening in which the oxygen barrier film is exposed; a lower electrode formed to follow bottom and wall surfaces of the opening formed in the second interlevel dielectric film and to be connected to the oxygen barrier film; a capacitive insulating film formed on the lower electrode, following the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has contiguous portions located over the bottom and wall surfaces of the opening, respectively, to form a U-bent portion that extends along the direction in which the conductive plug penetrates through the first interlevel dielectric film.
In the second inventive semiconductor device, the lower electrode is formed to follow the bottom and wall surfaces of the opening formed in the second interlevel dielectric film. Thus, a U-bent portion extending along the direction of penetration of the conductive plug is formed in contiguous portions located over the wall and bottom surfaces of the opening. Accordingly, the capacitive insulating film has a face substantially perpendicular to the substrate surface. As a result, the same effect as in the first inventive semiconductor device is obtained.
The second inventive semiconductor device may include an adhesion layer that enhances the adhesion of the lower electrode to the second interlevel dielectric film and is interposed between the bottom surface of the opening and the lower electrode and between the wall surface of the opening and the lower electrode.
Alternatively, the second inventive semiconductor device may include an adhesion layer that enhances the adhesion of the lower electrode to the second interlevel dielectric film and is interposed between the wall of the opening and the lower electrode.
In such a case, the adhesion layer is preferably made of a metal oxide.
A third inventive semiconductor device includes: a conductive plug formed through an interlevel dielectric film formed on a substrate; a conductive oxygen barrier film formed on the interlevel dielectric film so as to be electrically connected to the conductive plug and to cover the conductive plug; a lower electrode having a relatively large thickness and formed on the oxygen barrier film so as to be connected to the oxygen barrier film and to cover the oxygen barrier film; a capacitive insulating film formed on upper and side surfaces of the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has contiguous portions located over the upper and side surfaces of the lower electrode, respectively, to form an inverted U-bent portion that extends along the direction in which the conductive plug penetrates through the interlevel dielectric film.
In the third inventive semiconductor device, the conductive plug, the oxygen barrier film and the lower electrode are stacked, and the capacitive insulating film is formed on the tipper and side surfaces of the lower electrode having a relatively large thickness. Thus, an inverted U-bent portion extending along the direction of penetration of the conductive plug is formed in contiguous portions located over the upper and side surfaces of the lower electrode. Accordingly, the capacitive insulating film has a face substantially perpendicular to the substrate surface. As a result, the same effect as in the first inventive semiconductor device is obtained.
A fourth inventive semiconductor device includes: a conductive plug formed through an interlevel dielectric film formed on a substrate; a conductive oxygen barrier film formed on the interlevel dielectric film so as to be electrically connected to the conductive plug and to cover the conductive plug; an underlying film formed on the oxygen barrier film and having a relatively large thickness; a lower electrode formed on upper and side surfaces of the underlying film, an end portion of the lower electrode being connected to the oxygen barrier film; a capacitive insulating film formed on the lower electrode, following the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has contiguous portions located over the upper and side surfaces of the underlying film, respectively, to form an inverted U-bent portion that extends along the direction in which the conductive plug penetrates through the interlevel dielectric film.
In the fourth inventive semiconductor device, the lower electrode is formed on the upper and side surfaces of the underlying film, and the capacitive insulating film is formed to follow the lower electrode. Thus, an inverted U-bent portion extending along the direction of penetration of the conductive plug is formed in contiguous portions located over the upper and side surfaces of the underlying film. Accordingly, the capacitive insulating film has a face substantially perpendicular to the substrate surface. As a result, the same effect as in the first inventive semiconductor device is obtained.
The fourth inventive semiconductor device preferably includes an adhesion layer that enhances the adhesion of the lower electrode to the underlying film and is interposed between the underlying film and the lower electrode.
In such a case, the adhesion layer is preferably made of a metal oxide.
A fifth inventive semiconductor device includes: a conductive plug formed through an interlevel dielectric film formed on a substrate; a conductive oxygen barrier film formed on the interlevel dielectric film so as to be electrically connected to the conductive plug and to cover the conductive plug; a lower electrode in the shape of a bottomed cylinder formed on the oxygen barrier film to be connected to the oxygen barrier film; a capacitive insulating film formed on the lower electrode, following the bottom surface of, and sidewall inner and outer surfaces of, the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has at least contiguous portions located over the bottom of, and the sidewall inner wall surface of, the lower electrode, respectively, to form a U-bent portion that extends along the direction in which the conductive plug penetrates through the interlevel dielectric film.
In the fifth inventive semiconductor device, a U-bent portion extending along the direction of penetration of the conductive plug is formed in contiguous portions located over the bottom and sidewall inner surface of the lower electrode. Accordingly, the capacitive insulating film has a face substantially perpendicular to the substrate surface. As a result, the same effect as in the first inventive semiconductor device is obtained. In addition, the lower electrode has the shape of a bottomed cylinder. Thus, the sidewall outer surface of the lower electrode increases the area in which the lower electrode faces the upper electrode, thereby increasing the capacitance significantly.
A sixth inventive semiconductor device includes: a conductive plug formed through an interlevel dielectric film formed on a substrate; a conductive oxygen barrier film formed on the interlevel dielectric film so as to be electrically connected to the conductive plug and to cover the conductive plug; a shape-sustaining film in the shape of a bottomed cylinder formed on the oxygen barrier film; a lower electrode formed on the shape-sustaining film, following the bottom surface of, and sidewall inner and outer surfaces of, the shape-sustaining film, an end portion of the lower electrode being connected to the oxygen barrier film; a capacitive insulating film formed on the lower electrode, following the lower electrode; and an upper electrode formed on the capacitive insulating film, following the capacitive insulating film. The capacitive insulating film has at least contiguous portions located over the bottom and sidewall inner surfaces of the shape-sustaining film, respectively, to form a U-bent portion that extends along the direction in which the conductive plug penetrates through the interlevel dielectric film.
In the sixth inventive semiconductor device, the lower electrode is formed on the shape-sustaining film in the shape of a bottomed cylinder formed on the oxygen barrier film, so that the lower electrode follows the bottom surface and the sidewall inner and outer surfaces of the shape-sustaining film. In addition, the capacitive insulating film is formed to follow the lower electrode. Thus, a U-bent portion extending along the direction of penetration of the conductive plug is formed at least in contiguous portions located over the bottom and sidewall inner surfaces of the shape-sustaining film. Accordingly, the capacitive insulating film has a face substantially perpendicular to the substrate surface. As a result, the same effect as in the first inventive semiconductor device is obtained. In addition, the shape-sustaining film having the shape of a bottomed cylinder is used. Thus, the capacitance increases, while the shape of the lower electrode is stabilized.
In such a case, the shape-sustaining film is preferably made of a metal oxide.
In the first through sixth inventive semiconductor devices, the capacitive insulating film is preferably made of a ferroelectric or a high-dielectric-constant material.
A first inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming a conductive oxygen barrier film on the first interlevel dielectric film such that the conductive oxygen barrier film covers the conductive plug; d) forming, on the first interlevel dielectric film, a second interlevel dielectric film having an opening in which the oxygen barrier film is exposed; e) forming a lower electrode on bottom and wall surfaces of the opening formed in the second interlevel dielectric film such that the lower electrode is connected to the oxygen barrier film; f) forming a capacitive insulating film on the lower electrode such that the capacitive insulating film follows the lower electrode; and g) forming an upper electrode on the capacitive insulating film such that the upper electrode follows the capacitive insulating film.
In the first inventive method, a capacitive insulating film has a face substantially perpendicular to the substrate surface over the wall surface of an opening formed in a second interlevel dielectric film. Thus, it is possible to reduce the projected area of a capacitor onto the substrate surface, while ensuring a required capacitance. In addition, a lower electrode is formed on the bottom and wall surfaces of the opening in the second interlevel dielectric film. Thus, the thickness of the lower electrode can be easily reduced, thus ensuring a large surface area of the lower electrode. Furthermore, since an oxygen barrier film is formed independently of the lower electrode, the oxygen barrier film can be made relatively thick. Thus, even if the capacitive insulating film is made of a ferroelectric or a high-dielectric-constant material, the conductive plug is hot oxidized during crystallization of the ferroelectric or the like through heat treatment.
In the first inventive method, the step e) preferably includes the step of removing part of the lower electrode located on the second interlevel dielectric film by, for example, a CMP process or a resist etch back process.
The first inventive method may include the steps of forming, on parts of the second interlevel dielectric film respectively located on the bottom and wall surfaces of the opening, an adhesion layer that is connected to the oxygen barrier film and enhances the adhesion of the lower electrode to the second interlevel dielectric film, between the steps of d) and e).
Alternatively, the first inventive method may include the step of forming, on part of the second interlevel dielectric film located on the wall of the opening, an adhesion layer that enhances the adhesion of the lower electrode to the second interlevel dielectric film, between the steps of d) and e).
In such a case, the adhesion layer is preferably made of a metal oxide.
A second inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming, on the first interlevel dielectric film, a second interlevel dielectric film having a first opening in which the conductive plug is exposed; d) forming a conductive oxygen barrier film in the first opening such that the conductive oxygen barrier film fills in the first opening; e) forming, on the second interlevel dielectric film, a third interlevel dielectric film having a second opening in which the oxygen barrier film is exposed; f) forming a lower electrode on bottom and wall surfaces of the second opening formed in the third interlevel dielectric film such that the lower electrode is connected to the oxygen barrier film; g) forming a capacitive insulating film on the lower electrode such that the capacitive insulating film follows the lower electrode; and h) forming an upper electrode on the capacitive insulating film such that the upper electrode follows the capacitive insulating film.
In the second inventive method, the same effect as in the first inventive method is obtained. In addition, an oxygen barrier film is formed to fill in a first opening formed in a second interlevel dielectric film. Thus, even if the oxygen barrier film is made of a difficult-to-etch material, the oxygen barrier film is formed easily. In addition, the oxygen barrier film is easily made thick, thus ensuring an enhanced barrier property.
In the second inventive method, the step f) preferably includes the step of removing part of the lower electrode located on the third interlevel dielectric film.
The second inventive method may include the step of forming, on parts of the third interlevel dielectric film respectively located on the bottom and wall surfaces of the second opening, an adhesion layer that is connected to the oxygen barrier film and enhances the adhesion of the lower electrode to the third interlevel dielectric film, between the steps of e) and f).
Alternatively, the second inventive method may include the step of forming, on part of the third interlevel dielectric film located on the wall of the second opening, an adhesion layer that enhances the adhesion of the lower electrode to the third interlevel dielectric film, between the steps of e) and f).
In such a case, the adhesion layer is preferably made of a metal oxide.
A third inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming a conductive oxygen barrier film on the first interlevel dielectric film such that the conductive oxygen barrier film covers the conductive plug; d) forming a second interlevel dielectric film on the first interlevel dielectric film such that the oxygen barrier film is exposed from the second interlevel dielectric film; e) forming, on the exposed oxygen barrier film, a lower electrode having a relatively large thickness; f) forming a capacitive insulating film on upper and side surfaces of the lower electrode; and g) forming an upper electrode on the capacitive insulating film such that the upper electrode follows the capacitive insulating film.
In the third method, the capacitive insulating film has a face substantially perpendicular to the substrate surface over the wall surface of the lower electrode. Thus, it is possible to reduce the projected area of the capacitor onto the substrate surface, while ensuring a required capacitance. In addition, a lower electrode having a relatively large thickness is formed after the formation of an oxygen barrier film. Thus, processing can be easily performed, as compared to the case where the lower electrode and the oxygen barrier film are formed simultaneously. Further, a second interlevel dielectric is formed such that the oxygen barrier film is exposed from the second interlevel dielectric film. Thus, the second interlevel dielectric film is present around the lower electrode. Therefore, even if the lower electrode is larger than the oxygen barrier film, the lower electrode can be formed to overlap with the second interlevel dielectric film. As a result, the alignment between the oxygen barrier film and the lower electrode is performed easily.
A fourth inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming a conductive oxygen barrier film on the first interlevel dielectric film such that the conductive oxygen barrier film covers the conductive plug; d) forming a second interlevel dielectric film on the first interlevel dielectric film such that the oxygen barrier film is exposed from the second interlevel dielectric film; e) forming, on the exposed oxygen barrier film, an underlying film having a relatively large thickness; f) forming a lower electrode on upper and side surfaces of the underlying film such that an end portion of the lower electrode is connected to the oxygen barrier film; g) forming a capacitive insulating film on the lower electrode such that the capacitive insulating film follows the lower electrode; and h) forming an upper electrode on the capacitive insulating film such that the upper electrode follows the capacitive insulating film.
In the fourth inventive method, the same effect as in the third inventive method is obtained. In addition, since a thick member is used as an underlying film for a lower film instead of increasing the thickness of the lower electrode itself, it is possible to select a material exhibiting processability better than the lower electrode, and thus the yield is enhanced.
The fourth inventive method preferably includes the step of forming, on the surface of the underlying film, an adhesion layer that enhances the adhesion of the lower electrode to the underlying film, between the steps of e) and f).
A fifth inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming a conductive oxygen barrier film on the first interlevel dielectric film such that the conductive oxygen barrier film covers the conductive plug; d) forming a second interlevel dielectric film over the entire surface of the first interlevel dielectric film including the oxygen barrier film and then forming, in the second interlevel dielectric film, an opening in which the oxygen barrier film is exposed; e) depositing a conductive film on bottom and wall surfaces of the opening formed in the second interlevel dielectric film, thereby forming, on the oxygen barrier film, a lower electrode in the shape of a bottomed cylinder made of the conductive film and connected to the oxygen barrier film; f) removing part of the second interlevel dielectric film to expose the lower electrode and then forming a capacitive insulating film such that the capacitive insulating film follows sidewall inner and outer surfaces of the exposed lower electrode; and g) forming an upper electrode on the capacitive insulating film so that the upper electrode follows the capacitive insulating film.
In the fifth inventive method, the capacitive insulating film has a face substantially perpendicular to the substrate surface on the sidewall inner and outer surfaces of the lower electrode. Thus, it is possible to reduce the projected area of the capacitor onto the substrate surface, while increasing the capacitance significantly.
A sixth inventive method for fabricating a semiconductor device includes the steps of: a) forming a first interlevel dielectric film on a semiconductor region; b) forming, in the first interlevel dielectric film, a conductive plug connected to the semiconductor region; c) forming a conductive oxygen barrier film on the first interlevel dielectric film such that the conductive oxygen barrier film covers the conductive plug; d) forming a second interlevel dielectric film over the entire surface of the first interlevel dielectric film including the oxygen barrier film and then forming, in the second interlevel dielectric film, an opening in which the oxygen barrier film is exposed; e) forming a shape-sustaining film in the shape of a bottomed cylinder on bottom and wall surfaces of the opening formed in the second interlevel dielectric film; f) removing part of the second interlevel dielectric film to expose a sidewall outer surface of the shape-sustaining film, and then forming a lower electrode such that the lower electrode follows the sidewall outer surface of, and a sidewall inner surface of, the exposed shape-sustaining film and that an end portion of the lower electrode is connected to the oxygen barrier film; g) forming a capacitive insulating film on the lower electrode such that the capacitive insulating film follows the lower electrode; and h) forming an upper electrode on the capacitive insulating film such that the upper electrode follows the capacitive insulating film.
In the sixth inventive method, the same effect as in the fifth inventive method is obtained. In addition, a shape-sustaining film made of a material different from that used for the lower electrode is used as a bottomed-cylindrical member instead of using the lower electrode as the bottomed-cylindrical member. Thus, it is possible to prevent the bottomed-cylindrical member from being deformed.
In the sixth inventive method, the shape-sustaining film is preferably made of a metal oxide.
In the first through sixth inventive methods, the capacitive insulating film is preferably made of a ferroelectric or a high-dielectric-constant material.